Threading tool



Jan. 6, 1931. F. w. ROBERTSHAW THREADING TOOL Filed Feb. 16. 1927 2 Sheets-Sheet l Jan. 6, 1931. F. w. ROBERTSHAW THREADING TOOL Filed Feb. 16. 1927 2 Sheets-Sheet 2 Patented J an. 6,

" UNITED s ra FREDERICK w. noBERrsHAw, or ri'r'rsnuaen, rENNsYLvAmA HE-Jeanine TOOL Application filed February 16, 1927. Serial 163,571.

The present invention relates broadly to the art of metal working andmore )i11l7lCLllarly to an improved tool by means of. which threads may be quickly and accurately formed on any desired article, the tool preferably being of such construction that after a thread of initially predetermined cut on such article, to is made lmpossiblei length has been rthcr cutting operation This operat on is obtained without losing the settin'gof any of the tool parts.

The present adapted for use in short threads on ar the large diameter, such'as caps, plugs,

invention is particularly formation of relatively *ticles of comparatively closures,

and the like, although the utility of the invention is not limited It is customary,

6 present invention rela releasable threading are automatically collapsed or in this respect.

in the. art to which the to provide so-called in which the (lies expanded tes, dies after a predetermined threading operation, whereby the maxnnum length of thread is W definitely controlled. however, that while character operate at a high Experience has shown, tools of this general speed to cut threads of the length required, the cutting dies are not always original setting, with reset to exactly their the result that successivearticles have threads formed thereon differing in actual amounts var 'ung sandth of an inch inch. lVhilet this is tionable where a tapered overall diameter by from a fraction of a thouto several thousandths of an not particularly objecthread is being cut,

it is decidedly 'ObjBClHOHablGlH articles requiring a substantially stralghtthread; Also, with tools having hese general character1s- 4 tics, the, frequent adjustment offthe parts,

" together with the automatic release and resettingfor each thread-cutting operat1on,

soon produces .sufilcient 'looseness to prevent the subsequent precision operatloirthereof.

The present invention has for one of its objects the provision of a thread-cutting tool adapted to be initially set to cutja thread of the required diameter such setting for aslo 59 lnthisirespect the pr and therea ter, retain no; a pcriod'as desired.

escnt tool embodies the desirable characteristics of a hired threading die. 1 v 1 It is further desirable, however, to provide a tool in which adjustment'is possible at will, and one of the objects of the present invention is to providea tool in which the cutting dies may be easily adjusted to increase or decrease the diameter of the thread formed thereby. j

Still another object of the invention is to combine the foregoing characteristics in a tool capable of automatically releasing itself after a thread of the desired length has been cut thereby, such a tool being particularly adaptable'for use on a lathe or similar machine operating at a comparatively high speed; r i y In the accompanying drawings there is shown, for purposes of illustration only, a preferred embodiment of the present invention, it being understood that the drawings do not define the limitations of my invention,

as changes in the construction and operation I I perspective view of the knoclzon ring;

TBS EN Q FICE i 7 Figure 5 is anelevation of the regulating and adjusting ring; 7

Figure 6 is a detail sectional View, on an enlarged scale,on the line VI-VI of Figure 5 Figure 7 is a side elevation of the expand mg screwJfoi' the regulating and adjusting a;

Figure 8 is aside elevational view of the 'clutchpinj; and l Figure 9 is-a transverse sectional view on the ,elX lX of Figure 2. .In carrying out the present, invention,

theremay be provided a supportingarbor 2 of any des red construction,- havim: formed proved threading tool. J Surrounding the bearing-5 is a knockoff ring 6, illustrated inperspective in Figure 4c. This throughout plurality of die-receiving'grooves 11. Any

ring is formed'with an enlarged base portion 7 carrying one or more drl vinglugs 8 adapted to cooperate with the grooves or recesses 4-,

as illustrated in dotted lines in Figure 2. V The knockoff ring has an outer diameter such that it is adaptedto accurately fit within a diev head 9 and properlycenter the same, the die head and knockoff ring being held in assembler'l relation by means of one or more set screws or similar means 10.

The die head comprises a generally annular .body having formed therein and extending completely through the walls thereof a portion of its length only, a

number of such grooves may be formed in the 'headin accordance with the number of dies which it is desired to utilize for the threading operation. i I

After the knockoff ring 6 has been placed in position around the bearing portion 5, vthe clutch p1nl2, shown in detail in Figure 8, s slipped into position through a suitable opening in the arbor, and is held in the desired position by a set screw 13 adapted to engage a depression 14: in the pin. With these parts in position, the die head-may be slipped over the knockoff ring and secured thereto bythe screws 10. Thereafter a regulating and adjusting ring 15, havin an internal diameter substantially conforming to the outer diameter of the bearingportion 5, may be slipped over the bearing portion into the general position illustrated in Figure 2. This regulating and adjusting ring isdivided into a number of sections corresponding to the numberof die-receiving grooves 11 in the head 9. Inthe'embodiment illustrated in detail in Figure 5, these-sections are shown as being separated by axially extending grooves 16. Each of the sections is provided with threads 17 throughout the entire area thereof or throughout: any predetermined portion thereof. .Wl are the threads extend continuously, it is desirable to have certain portions thereof cut away to provide bearing zones 18. These bearing Zones-are adapted, when theregulating and adjusting ring is expanded, to bear against the insideof thedie head 9, as cleainy indicated in Figure 1.

V The threads on each section of the regulate ingz'and adjusting ring are formed so; that at one end they are closerfto the center'of the ring than they are attheopposite end, the

, rmaj'or portion ofthe length of the threads on each'section' forming a c am'elfective upon rotation to 'pro' ide a surface at varying dis threading die 19 is slipped 'tion thereof to engage the of thermg'and expand tances from the center of the ring for the purpose hereinafter more fully pointed out.

With the foregoing parts in position, a into position in each of the grooves 11 in the die head, These dies all have the same characteristics and each has a length materially greater than the length of the thread which it may be desired to form on a given article, such, for example, as the cap C indicated in chain lines in F ure 2; After the cutting dies have been ap{ proximately positioned in the grooves 11., each of the adjusting screws 20 is set up to engage. the back of its corresponding die and hold the same against outward displacement The screws 20 are carried by a supporting ring 21 which surrounds the die head and is held in position thereon by a suitable set screw 22. Byrotating the regulating and ad ustln rin 15 in one direction or the other, the extent to whichthe cutting dies 19 may be inwardly adjusted is varied. The

ring 15 will have threads thereon of exactly the same pitch as the threads 23 on the dies 19, whereby engagement between the threaded portions of each will properly adjust the cutting dies. This axial. adjustmentof the cutting dies will so position them that they will properly cooperate with the article to be threaded and each form threads in the proper position. After all the parts have been adjusted as desired, the expanding screw, 24: carried by the ring 15 'is threaded downwardly to cause the tapered head portapered walls 25 the same to lock it in position, this expansion being permitted by reason of the fact that the ring is split transversely as indicated at 26. V

In operation, after the tool has, been assembled, the arbor 2 is placed. in alathc or other machine, and the lathe operated to rotate the arbor, and by reason of the. lugs 8 to also rotate the knockoff ring .6 and the associated Parts; This condition will con tinue until the operator effects axial movement of the arbor 2 in a direction the reverse of that in which the knockofl ring 6 moved in figure' 2. This movement will bring the ends of the clutch pin 12,. which overlapsthe 7 ct disengagementof'the'lugs' 8 from r cesses l as lndlcated by the arrowrB lugs 27 on the face of the knockoff ring opposite the lugs 8. Prior to this time the direction of rotation of the arbor 2' will have been changed, so that when'the pin 12 engages thelugs27, the cutter assembly will be rotated in a direction tounscrew it from the thread which it has formed on the article being threaded.

tion of the work will effect a longitudinal movement of the cutting head assembly along the bearing portion 5 of the arbor un til such time as the lugs 8 become disengaged from the recesses 4:. After this dis- 7 engagement has taken place, the cutting head assembly will rotate freely with the work without performing any cutting oper- 'ation. This will continue until such time as the arbor 2 is moved in the direction of I into engagement the cutting head assembly I will be rotated in the reverse direction such that it will be unscrewed from the previously threaded work.

In either case the length of thread cut' may be variably controlled by placing any desired number of shims in the bottoms of the recesses 4-. The thicker the shims, the shorter the axial movement requiredto effectdisengagement of the lugs 8' from the recesses, and therefore the shorter the thread.

With the construction shown, should the thread which is out be of too great diameter,

the "screw 24 is loosened, the screws 20 backed off, the ring 15 rotated in aclockwise direction as viewed in Figure 1, and theparts again adjusted. Onthe other hand, if

the thread is of too small diameter, thering is rotated in the opposite direction.

Should any cutting die become broken I at any time,-its corresponding screw 20 may .be'backed off without releasing any of the other cutters, and a new cutter quickly placed in position.

The cutting dies are at all times rigidly held in a given position, insuring the formation of perfect threads, and by reason of the automatic action of the knockoff ring, these threadsmay be formed at high speeds without fear of breakage of the tool.

' WVhen cutting straight threads, the cutting dies may be sharpened without removal It will be apparent to those skilled in the,

from the die head by simply regrinding the outer ends thereof. This regrinding effects resharpening under'such conditions, for the reason that thefirst thread on each cutter affects the entire cutting operation. 'VVith such straight or parallel threads, the .face

or flat part ofv each of the cutters never' requires any regrinding. Vith tapered threads the cutters must necessarily be individually. removed and touched up on the face, as in such case all of the teeth throughout the lengthof the projecting portion of the cutters in engagement with an article at any giventime are effective on such'article. In any case, in. addition to the regrinding of the ends, they ,may be ground on the threaded faces to relieve the same to an extent necessary to facilitatestarting of the thread-cutting operation. I v

Certain advantages of the present invention arise from the use of a rigid tool easily adjusted and" capable of being operated at high speeds to effect av threadcutting operation throughout a predetermined part of an article. t Y

Other advantages arise from the provision of automatically stopping the cutting operation after a thread of the desired length has been out without the necessity of collapsing or releasing the cutters, or in any the cutting of straight or parallel threads they may be sharpened without removal;

I'clai'm: I I I I 1. In a thread-cutting tool, adie head, a plurality of individually adjustable threadcuttingdiesin said'l'iead,a regulating and adjusting ring cooperating with all of said dies, an arboron which saidhead is axially movable, andmeans for operatively connecting said head and arbor'at the limit of movement of the head on direction. y i I 1 v 2. In a thread-cutting tool, a-die head carrying'afpluralityof adjustable cutting dies, means for rigidly maintaining said dies'i'n adjustedposition, a driving arbor for said head, and a knockoff ring having means pro Vidiiig a driving connection between "said arbor'and said'head and effective for releas ing said; headfrom said arbor after athread of initially predetermined length has been jcut by saidhead, said knockoff ring and said arbor being provided with other inter-en gaging parts adapted to beenga-ged toeffect removal of saidcutting dies from a threaded article. i

thearbor in either first-mentioned portion to provide a driving 7 engagementbetyveen the arbor and the knockoff, and said arbor and knockoff each having other offset portions adapted to provide a second, driving engagement tlierebe'tiveen,

' the respective offsets beingengageable at Will by relative axial movement between the arbor andtl e knockoff. 7

j 4. In a thread cutting tool, an arbor hav- 7 ing an offset portion, a knockoff member having'an offset portion adapted to engage said first-mentioned portion to-provide a driving engagement between the arbor and the knockoff and said arbor and knockoff each having other offset portions adapted to provide a second driving engagement therebetween, the respec'tiveoffsets being engageable at will by relative axialmovement between the arbor and the knockoff, said knockoff. comprising a ring-shaped member surrounding the arbor intermediate the offset portions thereon, and movable therebetween. v

5. In a thread cutting tool, a driving arbor, a die head carrying a plurality of adjustable cutting dies and rotatably mounted on said fllYbOI,'I1'l62tl1S for rigidly maintaining said 'dies in adjusted position, and a knock-off ring surrounding said arbor and constituting a driving connection between sald arborand head and efiective for releasing said head from said arbor after a thread of'initially predetermined lengtlrlias been cut by said head, said arbor having other means adapted to engage said ring after a thread of predetermined length has been cut and'rotate said head in a direction opposite to its threads cutting direction when the arbor is rotated to back off the tool. V

p 6. In a thread cutting tool, an arborhav ing axially spaced driving means thereon, a knock-off member movable axially of thearbor for engagement with either of said driv-,

bor and radially into overlapping relationship to the knock-,ofimemberto exert a backing off pull thereon.

In testimony whereof I havehereunto set my hand. V

FREDERICK W. ROBERTSHAXV. .7

ing means at Will, saidknock-oif member be-v mg driven entirely by Sll{l arbor,-'and a threading means operatively"connected to said knock-off member and continuously rotated thereby when said member is rotated, one of said driving means extendingtransverselyofthea-rbor and radially wa mer lapping relationship to the knock-off member to exert a backing off pull thereon.

i 7. In a thread-cutting tool,ran arbor having axiallyspaced driving means thereon, a ring' shaped knock-off member surrounding the arbor and axially movable along thearrbor for engagement With either'of said driving means at Will, said knock-off member being i driven entirely by said arbor, and a threading means operativelyfconnected to said knork-.- off member and continuously rotatedthereby WVllGIl said memberisrotated, one of said driv mg means extending transversely of the ar- 

